Carboxylic acid functional groups are present in a wide variety of compounds including amino acids, pharmaceutically active compounds, polymers, etc. Carboxylic acids are also used in many solid-phase synthesis to form esters, amides, and other carbonyl linkages. In addition, carboxylic acid functional groups are used to form a wide variety of different functional groups. However, in many instances when a carboxylic acid functional group is present in the molecule, it can interfere with other desired reactions. In these instances, the carboxylic acid group is protected to avoid undesired side reactions.
While there are a variety of protecting groups available for carboxylic acids, each has different reactivity and use. In many instances, it is desirable to be able to remove the carboxylic acid protecting group selectively or simultaneously in the presence of other functional group protecting groups. This is especially true in syntheses of target molecules that require multiple different protecting groups. If one can remove several protecting groups in a single reaction, it would reduce the time and cost of synthesis of target compound.
The widely utilized protecting groups for alcohol (e.g., diol) compounds are cleavable ether or silyl ethers or esters via acidic or basic conditions. Acetal is a typical protecting group for carbonyl molecules. Carboxylic acids are generally protected as their esters or orthoesters. There are many instances in organic synthesis where simultaneous or “one-pot” removal of protecting groups is needed or desired. Unfortunately, there are limitations of available carboxylic acid protecting groups and/or deprotection conditions that allow such one-pot removal of carboxylic acid protecting group with other protecting groups for alcohols or amines or carbonyls.
Therefore, there is a need for novel protecting groups which can be used in a variety of applications, including carboxylic acid protecting groups, linkers for solid-phase organic synthesis, etc., that can react with carboxylic acid functional group and allow for removal under a relatively mild conditions.